Oracle

descriptionA database trigger is a stored PL/SQL program that is associated with a table. Whenever a particular data manipulation statement (Insert,update,delete) is emitted on a specified table, Oracle automatically executes the sequence of

3. External connectionAn outer join is a result set in which a record in a join table that does not conform to a join condition is added on the basis of an inner connection. The outer joins are divided into left outer connection, right outer

Learning Goals:? usingequivalentAndnot equivalentThe connection queries the data in multiple tables in the SELECT statement. Useself-connect。 UseExternal ConnectionQuerying for data that does not meet the join criteriaOracle ConnectivityEquivalent

First we query all the tables under the Oracle userSELECT * FROM All_tab_comments--Query All users ' tables, views, etc.SELECT * FROM User_tab_comments--Query the user's table, view, etc.SELECT * FROM All_col_comments--queries the column names and

1. Creation of three filesExp.list content:user name and password forOracle DatabasePwdExp.log is primarily used to store log information when the database is automatically backed upexp.sh#!/bin/SH#找到数据库的路径export oracle_base=/u01/app/Oracleexport

1. Create a tableNo constraintCREATE TABLE T_user (ID number,--type is number typeName Varchar2 (),--varchar2 () can varyGender char (2),Birthday Date Default sysdate is the current day)Plus constraintsCREATE TABLE T_user2 (ID number,Name VARCHAR2

The purpose of the UNION directive is to combine the results of two SQL statements to see the results of the query you want.For example:SELECT Date from Store_informationUNIONSELECT Date from Internet_salesNote: In the Union usage, the field types

Index unique Scan: is a large scan for a unique index, it only applies to the destination SQL where the query is equivalent in the Where condition, because the scanned object is a unique index, scanning only the index height so many index blocks are

1.oracle sign-in and logoutGo to cmd command line:Login to normal user--1) sqlplus scott/169500 Note: Scott is the user name (this is the Oracle comes with the user) 169500 is the password2) Sqlplus drawdownEnter user name: ScottEnter Password: 16950

First, some conceptsDefined:Primary Key-uniquely identifies a record, cannot be duplicated, is not allowed to be emptyForeign key--the foreign key of the table is the primary key of another table, the foreign key can have duplicate, can be a null

Triggers are stored as separate objects in the database, and unlike stored procedures, stored procedures start running through other programs, and triggers are started by an event. 1. Trigger characteristics 1> triggers are automatically run when an

In 12C, when a column is defined as "invisible," the SQL statement without direct access to the column is unable to see the "invisible column", and the statement that explicitly references the "invisible column" can access and manipulate the

Oracle provides the ability to store PL/SQL blocks in a database and to run it anywhere, a PL/SQL program block called a stored procedure or function.The difference between stored procedures and functions: the function needs to return data to the

? user-defined tables:– A set of tables that users create and maintain themselves– Contains the information required by the usersuch as:SELECT * from user_tables; View User-created tablesCREATE TABLE Statement? must have: –create Table permissions

First step (Connect to Oracle):In the DOS interface (below is the DOS interface operation) input: Sqlplus sang/12345 (here User name and password to write casually) @orcl as SysdbaSecond step (create user and authorize):Create user user1 (user name)

Oracle Learning Note onepermissions are divided into sysdba,nomal, the system comes with two users , the starting password is empty . the user is: System,sys. Login SYSTEM should use sysdba permissions to log in, if you forget the password, open the

Hot weather, weekend at home knocking at the code to find a strange SQL, when using the LEFT JOIN table to join the query, a to go to join B, before the order of a table row, suddenly confused, the first row of records ran to the end, before the

Three types of collection operations are available in Oracle: and (UNION), intersection (INTERSECT), poor (minus) UNION: Combine the results of multiple queries into one query result and remove duplicate values UNION All:

Regular Expression, Regular Expression Oracle also supports regular expressions, mainly embodied in the following five functions: REGEXP_COUNT, REGEXP_INSTR, REGEXP_REPLACE, REGEXP_SUBSTR, REGEXP_LIKE. Later, I checked the official Oracle

Ora-01034, ora-27101 troubleshooting Error cause: Solution: ora-27101 There may be 2 scenarios, which may lead you to encounter ORA-271011) Invalid ORACLE_HOME and ORACLE_SID (configured in environment variables)2) Database is down (check